Bob Carver ‘Black Magic’ VTA 20S Power Amplifier Review

October 10, 2012

Bob Carver has been a legend in the high-end audio world for four decades, beginning with his design of the Phase Linear 700 350 watt/channel amplifier in the 1970′s, his transfer function informed amplifiers mimicking the sound of other state of the art amplifiers (and fooling editors of The Audio Critic and Stereophile) marketed under his own name in the 1980s, and his line of Sunfire amplifiers and subwoofers in the 1990s. Recently he has returned to his first love, designing tube amplifiers, and has a new start-up named, fittingly, Bob Carver LLC, with the tagline The Vacuum Tube Amplifier Company. The past two years have seen the introduction of the Black Beauty 305 monoblock amplifier ($12,900/pair) and the Cherry 180 monoblock amplifier ($7400/pair), both of which have been met with enthusiastic reviews. He has even found time to introduce the Amazing Line Source Loudspeaker ($22,000), a significant refinement of his Amazing Loudspeaker design of the 1980s. Bob Carver is truly enjoying a renaissance.

The subject of this review is the brand new Black Magic 20, also known at the VTA20S, a 20 watt/channel stereo power amplifier which is offered at the eminently affordable price of $2100. For a tube amplifier, it comes in a small, 17 pound package, with its black chassis with silver fleck and silver trim occupying a space just 13” wide x 9” deep x 7” high. There are no front panel controls. The top of the chassis, in addition to holding a pair of 12AX7Bs and a quad compliment of EL84Ms, along with the interleaved output and power transformers, sports a gain control. When used with a preamplifier, the gain control is turned to the fully clockwise position; however, if you have but a single source, you can dispense with a preamplifier altogether, and use the gain control as a volume control, adding to its versatility.

Around back are a power switch, an ungrounded IEC inlet, two fuse holders, a pair of RCA input jacks and two pair of five-way bindings posts. In addition, there is a switch which lets you operate the Black Magic 20 as a 40 watt monoblock. If you like what one does for your system, adding a second one provides a logical upgrade path, doubling your pleasure, and giving you the opportunity to mate the amplifiers with a broader selection of less efficient loudspeakers.

Though its industrial design lacks a sense of the dramatic, the fit and finish of the Black Magic 20 is high. Construction consists of point-to-point hand wired axial and radial leaded components with star grounds. Component selection includes wire wound and metal film resistors, and metal polyester capacitors. The EL84Ms are Sovteks and the 12AX7Bs are sourced from Shuguang. A screen voltage regulator and DC restoration circuit minimizes crossover distortion and output tube power dissipation. The Black Magic 20 also features auto biasing and low idle current to increase output tube life.

I asked about output tube selection. The choice of EL84Ms is somewhat unusual. Usually designers will go with EL34s or KT88s. While those tubes provide greater power, they also require larger transformers, hence a more expensive design. In addition, the EL84s have long been one of Bob’s favorite tubes for their seductive sound. He is not alone; a great many guitar amplifier designers also have a soft spot for them. He chose the M models so he could get a higher plate voltage, and hence more power, out of a pair without red-plating them. They are used in a push-pull configuration.

I initially had the Black Magic 20 set up with the planar-magnetic Magnepan 1.7s, and, while it would certainly drive them, ultimately it wasn’t up to the task of doing so effortlessly, which is unsurprising given their extremely low efficiency and demanding load. There is a reason Magnepan always pairs its speakers with high-powered solid-state amplifiers at audiophile shows. They just aren’t happy unless they have a couple of hundred watts at their disposal. I shifted instead to the 88.5 dB sensitive Silverline Minuet Supreme Plus stand-mounted monitors (review forthcoming). Once paired with something more efficient, the Black Magic 20 come into its own.

I first put on Ann Sophie Mutter playing Beethoven’s Violin Sonata No. 5 in F major, Op. 24 “Spring” to get a sense of string tone. I noticed at the outset that the soundstage was wide, though somewhat shallow. This characteristic placed the violin up close. The Black Magic 20 provided plenty of detail. You could easily hear the bow traversing the strings. The midrange was only slightly toward the warm side of neutral. This is a tube amp that doesn’t sound like a prototypical tube amp. If you are looking for lushness and bloom, you will be disappointed. Instead, the amplifier paints a very well-delineated soundstage, with a slightly forward tone, which provides an excellent sense of tension and dynamics. Pizzicati jumped out at you, as did the piano accompaniment, which often appears recessed. The Black Magic 20 sounds like a very fast amplifier, with pace, rhythm and timing on the leading edge. This gave the performance a real sense of anticipation and excitement. There was no chance of falling into reverie while listening.

The same sense of tension and jump was evident on Bartok’s Suite for Piano, Op. 14 performed by Zoltan Kocsis. Here the soundstage was less wide but deeper than in the Beethoven recording. From a more distant perspective, the piano shrank in size, moving the perceived listening position further back in the orchestra section. The left hand plays a greater role in this work than in the previous violin accompaniment, giving the opportunity for the Black Magic 20 to demonstrate is bass handling capability. I must say I found it somewhat light, but again fast and articulate. It lacked the deeper, resonant quality of my more powerful solid-state reference. They were simply different, each enjoyable. Right hand notes lacked any tendency toward clanginess, while at the same time not giving up any of the high frequency tone or detail. Being sensitive to hardness in the upper midrange and treble, I never had the urge to turn the volume down, which can happen when that portion of the frequency spectrum is over-emphasized.

I also listened to Cyrus Chestnut’s fabulous jazz album Soul Food. On the opening cut, the trumpet, trombone, and saxophone all sounded polished rather than burnished, with a very bright and lively horn sound. Cymbals, however, did not have any sort of etched quality. If anything, the were somewhat muted. The soundstage was between the speakers, though each instrument was distinctly placed. The piano was light and lively. With all instruments playing all out, there was only the slightest hint of congestion in a complex soundfield. On Chestnut’s solo rendition of Swing Low, Sweet Chariot, the piano have a lovely, liquid tone. The lower midrange and bass, which I thought may have been somewhat lacking on other material, was here satisfying. Overall, I thought the piano was perhaps a bit de-focused, something immediately remedied in the next cut, indicating an aesthetic choice on the part of the recording engineer rather than a shortcoming with the Black Magic 20.

On a lark, I decided to make up a 1/4″ stereo jack to banana plug adapter and drove my Etymonic ER-4S in-ear headphones from the speaker terminals. The Etymonic ER-4S are a high impedance design requiring watts rather than milliwatts to drive properly. The Black Magic 20 did a remarkable job as a headphone amplifier. The noise floor was very low and the dynamics outstanding. Bob Carver could add icing to the cake by providing a headphone jack on the front panel. There’s an empty spot calling out for one on the right. And lest you think I’m crazy, my mastering instructor uses a Bryston power amp for his headphones, and he has over 200 gold and platinum records and 10 Grammys to his credit.

Conclusion

The Black Magic 20 is a diminutive tube amplifier which limits itself to 20 watts per channel in favor of a sweet and lively sound. No lush mush here. It is also extremely versatile, serving triple duty as a stereo power amplifier, a monoblock amplifier, and a single input integrated amplifier. With the right adapter, it can serve as a headphone amplifier as well. Such all around performance is rare. At $2100, it more than holds its own with similarly priced tube offerings. Paired with an efficient pair of loudspeakers, it can serve as the centerpiece of a very musical system. You owe it to yourself to audition it.

- Frank Berryman

Contact Information

Bob Carver LLC
204 Industry Drive, Suite F
Nicholasville, KY 40356
Telephone: (859) 258-9794
www.bobcarver.com
[email protected]

Associated Equipment

Analog Sources: VPI Scout; Dynavector 20X2; Musical Surroundings Phonomena II
Digital Sources: Meridian G08; Mac Mini; Wadia 121; Halide Design Bridge and DAC HD; Amarra and Pure Music
Preamplifier: Meridian G02; Meridian G68ADV
Power Amplifier: Meridian 557
Loudspeakers: Magnepan 1.7, Meridian DSP5500s; Silverline Audio Minuet Supreme Plus
Analog Cables: Kimber Select KS1016 and KS1116
Digital Cables: Kimber D60; Meridian Digital Link; Wireworld Starlight USB
Speaker Cables: Kimber Select KS6063 and KS9033
Power Cables: Kimber PK10G and PK14G
Headphones: Etymotic ER-4S
Accessories: GIK acoustic treatments; dedicated 20 amp circuit; Audience aR2p power conditioner